These directions are no longer current but support the versions of Droogle prior to version 7.x-4x.
Make sure to see the readme file in the Droogle files folder but here are some tips: To configure what file types Droogle file upload will accept: http://drupal.org/node/1559764#comment-5955428 Annoyingly I agree you have to edit Droogle/Zend/Gdata/Docs.php and add the filetypes that are allowed for upload. Here is my current list.
private static $SUPPORTED_FILETYPES = array(
'PDF'=>'application/pdf',
'JPG'=>'image/jpeg',
'PNG'=>'image/png',
'GIF'=>'image/gif',
'TXT'=>'text/plain',
'CSV'=>'text/csv',
'TSV'=>'text/tab-separated-values',
'TAB'=>'text/tab-separated-values',
'HTML'=>'text/html',
'HTM'=>'text/html',
'DOC'=>'application/msword',
'DOCX'=>'application/msword',
'ODS'=>'application/vnd.oasis.opendocument.spreadsheet',
'ODT'=>'application/vnd.oasis.opendocument.text',
'RTF'=>'application/rtf',
'SXW'=>'application/vnd.sun.xml.writer',
'XLS'=>'application/vnd.ms-excel',
'XLSX'=>'application/vnd.ms-excel',
'PPT'=>'application/vnd.ms-powerpoint',
'PPS'=>'application/vnd.ms-powerpoint');